1. Technical Field
One or more embodiments of the present invention generally relate to power management. In particular, certain embodiments relate to managing power in computing systems.
2. Discussion
As the trend toward advanced central processing units (CPUs) with more transistors and higher frequencies continues to grow, computer designers and manufacturers are often faced with corresponding increases in power and energy consumption. Furthermore, manufacturing technologies that provide faster and smaller components can at the same time result in increased leakage power. Particularly in mobile computing environments, increased power consumption can lead to overheating, which may negatively affect performance, and can significantly reduce battery life.
Because batteries typically have a limited capacity, running the processor of a mobile computing system more than necessary could drain the capacity more quickly than desired. Some modern mobile computing systems therefore attempt to conserve power by placing the processor in various low power/idle states when there are no instructions to be executed. As the low power states become deeper and deeper, more functionality within the processor is often lost. For example, one ultra low power state involves reducing the core voltage so low that there may be concern over data loss in the internal cache(s) of the processor. Therefore, when a processor is in this state, the internal caches of the processor may be flushed to system memory and snoops to the cache can be ignored and/or disallowed. While use of such a deep low power state can provide significant power savings, data transfers between various controllers and the system memory typically require snoops to the processor internal cache. As a result, the processor may be forced out of the low power state more often than desired.